This invention has utility in the excavating field and, most particularly, in the mining of coal formations.
More specifically, it is believed the invention will be especially useful when the method is used in conjunction with the type of cutter bits currently in use in the coal mining field and with the new type bit disclosed herein, and it is believed it will be a useful advance in the design of the machines used to reduce coal formations and, also, will be a useful advance in the methods used to reduce coal formations.
New methods and new machines are contemplated by the present invention.
By way of example, it is believed the invention can be used where point attack type cutter bits are now used in coal mining, especially when such point attack type cutter bits are being power driven through the formation being reduced, such as in coal mines.
Various types of machines have been and are known in the art for digging and reducing earth formations and, also, for the mining of minerals, such as coal and other deposits.
Machines predominantly used in the earth boring art are generally exemplified by those in use for oil well drilling and which generally comprise multiple cone type rollers, where conically shaped roller cones have blunt or dome shaped carbide compacts imbedded in their outer periphery.
The conically shaped roller cutters are mounted on convergent shafts on a frame on the lower end of the drill string and rotation of the drill string causes the rolling cutters to rotate and the compacts to hammer the bottom of the hole and fracture the material. Such machines are more fully described and best exemplified by U.S. Pat. Nos. 2,774,570 and 2,687,875.
Also, in the earth boring field, there are other machines known as tunnel boring machines or raise boring machines which utilize cylindrical rolling cutters which also have blunt carbide compacts imbedded in the cutters' outer periphery. These tunnel boring machines have cutters that are mounted upon a frame located on the lower end of a drill string, and rotation of the drill string while holding the cutters against the formation to be reduced will cause the cutters to rotate and the carbide compacts will impact and fracture the earth formation. These machines are more fully described, and may be exemplified by, U.S. Pat. Nos. 3,797,592, 3,734,213 and 3,679,009.
The machines presently in use for reducing coal formations generally are comprised of power driven rotary drums having cutter bits fixedly mounted on the periphery of each drum. In order to reduce and fracture the coal formation, the drum, and with it the cutter bits, are rotated under power and driven through the formation of coal, thereby fracturing the coal formation by both impact of the bit and friction of the bit as it is driven on through the formation.
Once the drum has been power driven through the formation, the coal falls to the floor of the mine under the machine and is, usually, scooped into a conveyor which will then remove the coal from the area.
In general, it has been found that the cutter bits used on such a drum are, preferably, the individually rotatable pick type bits which are comprised of a hard wear resistant point at the foremost end of the bit, such as a carbide point that initially impacts and fractures the coal seam. These point attack type cutter bits are used extensively in the mining and earth digging art and find particular application to the mining of coal formations. Such cutter bits are described in greater detail and best exemplified by U.S. Pat. Nos. 3,841,708, 3,854,056, 3,605,565, 3,519,309 and 3,499,685.
The desirable feature of these types of cutter bits is that they are held rotatably in a support block with the support block usually being mounted upon a power driven rotary drum or disc. When the bits rotate freely about their longitudinal axis in the holder, a self-sharpening effect occurs on the bit when engaged with the earth formations, and especially when used on coal formations.
The above-mentioned cutter bits are usually mounted so that the tips of the bits fracture the coal seam because of the initial impact and penetration of the carbide point and also continue to cut with a scraping action. There are, however, some drawbacks when using the cutter bits in that the cutting edges of the hardened tips are extremely brittle with the result that the tips frequently break off, particularly when the cutter is reversed or when encountering hard inclusions in a coal seam.
Further, when mining coal with currently known methods, the friction of dragging the bits through the slightly fractured or the unfractured formation increases the horsepower requirements of the machine and wears away the parent material of the steel bit surrounding and holding the carbide point. Further, the friction created by forcing the bits through the unfractured formations creates a severe amount of dust in the working area which creates unhealthy and hazardous working conditions within the coal mine.
With the presently known machines used in coal mining, and with the cutter bits presently known, there is a further danger that sparks created by the steel bits engaging in the coal seam could possibly cause an explosion of any mixture of dust and/or methane gas that may be in existence in the working area.
It is an object of the present invention to present a new and more efficient method of reducing earth formations, especially coal formations.
It is an object of the present invention to present new and improved machines for reducing earth formations, especially coal formations.
It is an object of the present invention to possibly reduce the horsepower requirements per ton of coal necessarily expended from an excavating machine, and especially from a coal mining machine.
It is a further object of the present invention to provide an apparatus and method of mining mineral formations, and especially coal formations, wherein the frictional engagement of the cutter type bits used to fracture the formations is reduced.
It is a still further object of the present invention to provide a method and apparatus for mining mineral formations, and especially coal formations, to reduce the sparking that may occur when the cutter bits are driven through the formation to be reduced.